This invention pertains to a zone control valve of the type used in hydronic temperature control systems.
Zone control valves are used to regulate the flow of fluids as a function of the fluid temperature. The valve opens or closes to control the flow volume in response to the temperature sensed by a thermostatic sensor.
One particular type of zone valve is taught by R. Weinstein in U.S. Pat. Nos. 3,711,060; 3,790,122; and 3,912,219. In the Weinstein arrangements, the body of the zone valve is installed in series with a fluid line and a drive assembly is slipped onto the valve body where it is "snapped" firmly in position. If the drive unit has to be removed, levers at each end of the unit are squeezed and the drive unit lifts from the valve body and seat assembly.
The seat assembly is spring loaded in the open position. When the drive unit is snapped onto the body, it depresses a pin which protrudes from the valve seat assembly thereby pressing a valve disc against a valve seat and preventing any flow through the valve.
To open the valve, energy is supplied to a heat motor which extends its piston to move a pivoting lever. As the lever rotates about its fulcrum, it operates electrical contacts, and allows the valve pin to be raised permitting the valve to open. A torsion spring coupled to the lever normally maintains the lever arm in a depressed position such that the valve is closed. As the heat motor operates, it works against the force of the torsion spring.